Converting Between Structs and Byte Arrays in Go
In Go, you may encounter situations where you need to convert between structs and byte arrays, or perform C-like operations such as type casting and memory copy. This article explores solutions for these tasks.
Type Casting
Go does not support C-like type casting, but you can use the unsafe.Pointer type to perform similar operations. To convert a struct to a byte array, use the unsafe.Pointer() function to convert the struct's address to a pointer:
<code class="go">type packet struct { opcode uint16 data [1024]byte } var pkt1 packet // Convert pkt1 to a byte array byteArray := (*[unsafe.Sizeof(pkt1)]byte)(unsafe.Pointer(&pkt1))</code>
To convert a byte array back to a struct, use the unsafe.Pointer() function again to cast the byte array pointer to the desired struct type:
<code class="go">// Convert byteArray back to a packet struct pkt2 := *(**packet)(unsafe.Pointer(&byteArray))</code>
Memory Copy
While Go does not have a direct equivalent of the memcpy() function, you can use the copy() function to perform memory copies. To copy the data from a byte array to a struct, you can use the following syntax:
<code class="go">type file_info struct { file_size uint32 // 4 bytes file_name [1020]byte } var file file_info copy(unsafe.Pointer(&file), pkt1.data) // Copy data from pkt1.data to file</code>
Using the encoding/binary Package
As an alternative to using unsafe.Pointer, you can use the encoding/binary package to handle type conversions between structs and byte arrays. This package provides functions for encoding and decoding data in binary formats, making it easier to handleendianness and data sizes:
<code class="go">// Convert a struct to a byte array t := T{A: 0xEEFFEEFF, B: 3.14} var buf bytes.Buffer binary.Write(&buf, binary.BigEndian, t) // Encode struct t to buf // Convert a byte array to a struct t2 := T{} binary.Read(&buf, binary.BigEndian, &t2) // Decode byte array buf into struct t2</code>
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